Barcelona striker Lionel Messi says he will defy his Spanish club's orders and join up with Argentina's Olympic squad this week.

The Argentina international has been at the centre of a tug of war between club and country with Barcelona trying to retain him for their Champions League qualifyier tie in August.

Messi, speaking before a FIFA judge declared that clubs were under an obligation to release their under-23 players for Beijing, said: "If FIFA say I should be there then I'll go without waiting for CAS (Court of Arbitration for Sport) ruling."

Barca have announced they will contest FIFA's ruling to CAS.

Messi added: "If CAS say that I have to return then I'll come back but for the moment I want to be with my country and my teammates."

The player has until Friday to link up with coach Sergio Batista's Argentina's Olympic squad in training in Japan.